There is currently an ongoing effort in the railway industry to develop electro-pneumatic brakes for railroad freight trains. It is generally acknowledged that such an electro-pneumatic brake control will enhance train operation by achieving a faster brake response, more equalized car retardation and a generally more uniform braking effort throughout a long train of cars.
These improved results are based on the assumption that all of the cars, or at least a majority of the cars, making up a train consist will be appropriately equipped for such electro-pneumatic braking, in which case direct braking cylinder pressure control is envisioned. With the exception of certain unit trains, however, it cannot currently be reasonably expected that any such majority of cars will be immediately implemented with the required electro-pneumatic equipment.
Accordingly, for the present, indirect brake cylinder pressure control is still extensively utilized. In this arrangement, the train brake pipe pressure is controlled at the locomotive and also at one or several remote cars throughout the train consist to accelerate reductions of brake pipe pressure in order to obtain a faster and more uniform brake response.
Presently, railroad trains are required to carry an end-of-train unit on the last car, which, among other functions, may be equipped to independently and remotely initiate a reduction of brake pipe pressure from the rear of the train in response to the operator activation of a special triggering device disposed in the locomotive. This is accomplished by transmitting an emergency brake application command signal from the locomotive to the end-of-train unit via radio communication.